The present invention relates to a method and a device for controlling operational sequences, particularly in a vehicle, at least one, sensor being connected to at least one control unit for controlling the operational sequences, and sensor information being transmitted to the control unit.
Today, vehicle sensors, particularly the sensors in the exhaust-gas branch, such as lambda sensors and hot-film air-mass meters, are frequently connected in a conventional manner via a cable harness to a control unit, particularly the engine control unit. Appropriate hardware lines are available for the signals and voltage supplies.
However, smart sensor technology having bus capability is indicated in the article by Heintz and Zabler xe2x80x9cEinsatzmxc3x6glichkeiten und Zukunftschancen intelligenter Sensoren im Kraftfahrzeugxe2x80x9d (xe2x80x9cUse Possibilities and Future Chances of Intelligent Sensors in the Motor Vehiclexe2x80x9d) from the BOSCH Technical Reports 1990, issue 52, pp. 30 through 41, which corresponds to the German version of the lecture at the SAE Conference in Detroit in March 1989. In the vehicle concepts in that context, multiple measurements of quantities are carried out which are needed by electronic systems in the motor vehicle. By adding electronic components, the corresponding sensors are provided with signal preprocessing and are given bus capability, i.e. are made multiply utilizable. A bus concept thereby develops in which intelligent sensors having electronics locally are connected to at least one control unit.
In order to couple sensors to a control unit with the aid of a bus system, particularly a CAN bus system, diverse time conditions are observed, particularly in the case of real-time-critical applications, for example, for sensors of the exhaust branch in connection with the engine control unit.
As a basis for determining such time conditions, for example, the German Published Patent Application No. 39 27 967 describes an electronic counter having a counting circuit and a frequency divider connected in series to this counting circuit. This so-called angle clock has the feature that the adjustable frequency divider weights a preferably constant frequency, supplied to its first input, with a factor whose magnitude is freely specifiable by a cycle-speed signal able to be supplied at any time intervals to a second input of the frequency divider; and the factor determining the divider ratio continually maintains its instantaneous value until a change occurs due to the feeding of a cycle-speed signal deviating with respect to the previous cycle-speed signal.
An object of the present invention is, with the aid of a synchronization element, particularly such angle clocks known from the related art, to implement an optimal or optimized synchronization of the sensor suite with the control unit or control device.
The present invention is based on a method and a device for controlling operational sequences, particularly in a vehicle, at least one sensor having a connection unit being connected via a bus system to at least one control unit for controlling the operational sequences, the control unit likewise having a connection unit, and sensor information being transmitted to the control unit, the control unit reading in and/or processing the sensor information at specifiable synchronization points. The respective synchronization points are advantageously ascertained in the control unit and in the sensor independently of one another by, in each case, a synchronization element in such a way with an allowance that the sensor information is available at the synchronization point for the control unit in a manner that it is able to be read in and/or processed.
In this context, the respective synchronization element is advantageously designed as an electronic counter having a counting circuit and a frequency divider connected in series to it, in particular as an angle clock.
By the use of one synchronization element each, particularly an angle clock, in the control unit and in the at least one sensor, a time gain advantageously results with respect to the sensor information to be transmitted to the control unit, since the sensors are able to start and end measurements of their own accord because they can fall back upon a separate time base.
Thus, as basic prerequisite for the description of a sensor bus, particularly for the exhaust branch, a synchronization of sensors and control unit is expediently implemented such that the sensor information is transmitted to the control unit, i.e. is available at the control unit, just when the control unit should also read in and/or process the control information. This is achieved primarily in that the respective synchronization points are ascertained by the respective synchronization element in such a way with an allowance which takes into consideration transmission tolerances, processing tolerances and other time and angle conditions, such that the sensor information is available at the synchronization point for the control unit.
This coordination can prevent unnecessary and too many signals transmitted via the bus system, and thus a lower bus load can be attained.
In contrast to applications in which a pure software synchronization signal is used and in which a multitude of high-priority messages can delay the transmission of the pure software trigger, which means the demands on the transmission time are no longer fulfilled, the use of the respective synchronization element, particularly angle clocks, has the advantage that control unit and sensors can be synchronized with high reliability and without delay with respect to the demands on the transmission time, the high topicality of the sensor information relative to a software trigger signal nevertheless being ensured.
If the sensor expediently contains a processing unit which preprocesses the sensor information, the allowance is advantageously predefined and/or adapted corresponding to the time for preprocessing the sensor information.
In one advantageous refinement, the allowance can be predefined and/or adapted in a variable manner, as a function of at least one performance quantity stemming from at least one operational sequence, in particular as a function of the engine speed, the wheel speed or velocity, etc. Thus, the dynamic influence of specific performance quantities assignable to operational sequences, particularly the engine speed, is advantageously taken into consideration.
The synchronization element of the sensor advantageously transmits a first quantity for ascertaining the synchronization point to the control unit, and the control unit compares this quantity to a second quantity of the synchronization element of the control unit for ascertaining the synchronization point, a correction quantity being generated therefrom by which the synchronization element is synchronized.
The allowance is advantageously predefined and/or adapted as a function of at least one of the following influences:
a transmission time from a processing unit of the control unit to its connection unit,
a transmission time or waiting time up to the termination of a bus message already transmitted via the bus system, until the sensor information or the first quantity and/or the correction quantity can be transmitted,
a transmission time of the first quantity and/or the correction quantity and/or the sensor information via the bus system,
a transmission time from the connection unit of the sensor to its processing unit,
a processing time until the end of the processing of the sensor information by the processing unit in the sensor and/or
a transmission time of the sensor information and/or of the first quantity from the sensor to the control unit, which includes the transmission time from the processing unit to the connection unit of the sensor and the transmission time from the connection unit of the sensor via the bus system to the connection unit of the control unit, as well as the transmission time from the connection unit of the control unit to the processing unit of the control unit.
The allowance is advantageously determined either in the form of a time quantity as a time allowance or in the form of an angle quantity as an angle allowance. Accordingly, the first and second quantity, as well as the correction quantity can represent a time quantity or an angle quantity.
In this context, the time allowance and angle allowance can be converted into one another. This conversion of the time allowance into an angle allowance and vice versa, taking into account the angular velocity, has the advantage that the performance quantity, particularly the engine speed, is calculated only at the synchronization point, since the instantaneous angle, especially the crankshaft angle, is available, for example, at an engine control unit, and therefore the synchronization point can be determined as a function of this angle information.
By using individual synchronization elements in the sensor and the control unit, an additional, cost-intensive hardware trigger line between the control unit and sensor can expediently be avoided.
In one advantageous refinement, the sensor information and the quantities for ascertaining the correction signal, as well as the correction quantity itself, are transmitted in a line-less manner between the connection unit of the at least one sensor and the connection unit of the control unit; in this advantageous refinement, the connection units are designed as transmitter/receiver units of a line-less bus system, particularly a radio bus system. This advantageously permits even greater savings on line links.